Remote control follow-up system for positioning a controlled unit by a control unit



Oct. 16, 1956 A. H. P. BLoMQvlsT ETAL 2,767,361 REMOTE CONTROL FOLLOW-UP SYSTEM FOR POSITIONING A CONTROLLED UNITv BY A CONTROL UNIT Filed June 13, 1952 M 55 37 39 i A T 4? T F ig: 5. fr MM-l' I I L52 NVENTURS.

BY ALL-u. may

ATTORNEY conventional remote `control devices,

nitecl States Patent s 2,767,361 REMOTE #CONTROL4 FOLLOW- UP SYSTEM non POSITIONING'A CONTRO LED UNIT BY CONTROL UNIT 11 claims. (cl. sis-s0);

This invention relates to follow-up systems for positioning a controlled unit by operation of Va control uni't'situated at a remote point. Y

While follow-up systems of this kind have useful applications, a now preferred field yof application of 4the invention is the aiming of a gun by remote control, pari ticulairly the control of the azimuth adjustment of the gun.

There are known for this purpose .remote Icontol `systems, the control unit and controlled unit'of whichfare each connected to a Vsignal generating; synchronizngde vice. Each of thesesynchronizing devices or selsyn unite comprises a stator .and la rotor so that when an A.-C. Yvfoltrage is supplied to the stator an output voltage is produced in the rotor winding the characterof whchdepends upon the angular position ofthe" rotor relative to the stator. By connecting the stators of the two devices anti-tapia@` ing an alternating voltage to the rotor lof one device a signal is obtained from the` rotor, "of other device. The former 'envelope fof this `signal depend'sjfpon 'he dii'erehce between the position of the controlled untahd the control unit, the position of thellatter un t'xrniining the final posi-:tion desired for "the controllo unit: The

signals obtained from the rotrsfof the lsynch'ijfd'fizei devices, which are in 'eiiect signal means, are fed th transmission means to drive mensopenat ely 'with the controlled unit for nio-ving `the"same desired position. These"trai1`smission means include A.C. amplifying means, phase detectih D.-C. amplifying means, and regulating for contro for control ofthe drive means: As will appear from the previous explanations,Ifo-f,the the,l positioning'. of the controlledfunit 'is eii'ected by a Vsignal the character or envelope of which determined 'by the relative ot'or position. An andysis of these `signals shows that it 'may contain p'ure sine Isignals both of high and low frequency. Experience shows that these sine signals, particularly `:those of hightfrequency, tend to cause disturbances by causing the system .to become selfeoscillating, Generally, thisvis the case when the amplification inthe system exceeds" a certain value; In other words, to avoid self-.oscillation of the system,the ampliiicationshould not exceeda c'ertin value which y'value infturn'is of cout-se determined by the lay-out of the specific system. Withsignalsv'of Vlow frequency, disturbances in the nature of self-oscilla tions do not. 'appealIl lso "that the ampl'iiication can be selected without regard to the `afo'rernentioned safe' maxi'- mumtvlue. Eiperience shows-that selfoscillatiens gen'- erally occur in the chain of` the components .of 'their-ans; mission means whenthe signals fed to the-said 4trahison's sion means have an Iamplificationequal'to one aphase from the phase Yangle Tof.=1 80 lfor whenthe ampliiication exceeds a certainvalhe at .a phase angle equalfto` 11809-1 -It is'not practical to. give deiinite vvalues of Ithepermissible deviation or amplification since thesevales scary displacement of more thanacrtain agleof .deviation ICC Y V2 can always be accurately and easily determined by methods `and steps well known for this purpose.

With remote control systems of the general type, herein referredto, it is desirable to use a relatively high ampli cation irrespectively whether or not the signals are of high frequency or of low frequency since a high ampliiication is necessary or at least advantageous for a rapid follow-up action of the controlled unit. Obviously, it is desirable -to move the controlled unit, such as a gun, as quickly as possibleinto its end position.

. It has already been proposed to associate the D.C. amplifying means with la filter network including in each series arm capacitance means connectedin parallel with resistance means and having a shunt arm including resistance means. A network of this type eiectsya certain positive vphase shift thereby moving the permissible maximum amplificati-on toward higher frequencies. However, it has been found that the phase shift eiected by a network of the aforementioned design not sufficient. Attempts have also been made to select the components of Ithe network so that the frequency at which thephase angle of occur-.s is increased. However, it was found that the increased frequency entailed a strong increase of theampliication in the networkwhich is highly vundesirable in view of possible self-Oscillationas previously pointed out. Accordingly, one of the :principal objects .of thevpresent invention is toprovide filter network means which eect I4phase angle .of 189 at a high frequency while limiting 4to t moderate and acceptable level the increase of the a'mpllication caused by the increase of the frequency. A more specific object of the invention is to provide filternetwork means which eiect a largerpositivephase shift within a narrow frequency range fand without substantally increasing the amplitude curve of the filter network means rat high frequencies.

Other and further objects, features and advantages -of the invention will be pointed out hereinafter `and set forth in `the appended claims forming part of the application. vIn the accompanying drawing several now preferred odiments of the invention are shown by way of Villustration and-n-ot by way of limitation.

' In the drawing: Y

Fig. 1 is a` diagrammatic view of a follow-up system according to the invention. n Fig. 4la `is a circuit diagram of the `selsyn units.

Fig. 2 is a circuit diagram of the lter network of Fig. l on an enlarged scale.

Figi. 3 is a circuit 'diagram of a modification of ,the

filter network.

Fig. 4 'is a circuit diagram of another modication of the filter network, and v l Fig. 'Sis a circuit diagram of still another nodication yofthe filter network. Referring rst toFigs. 1 and la in detaiLthe follow-up system according to this gure comprises a gun sight ,1 of conventional design. This sight constitutes' the control unit of the system and includes, among other Vcornponents, a control bow mounted for pivoting .about a ,horizontal axis and Vrotation about a vertical axis, pivoting about the horizontal axis serving to varyth'e e1evational position ofV the gun and rotation about -thefyertical axis lto vary the azimuth or 'lateral position of the gun. 'The latter adjustment is the one with which the system according to the invention is primarily concerned. rotation of Vthe control bow is transmitted by suitable coupling means diagammat-ically shown as a shaft l2, gears 3, 4 and ashaft 5 Vto a Vsynchronizing device -6. device or selsyn unit is of conventional design and should be vvisualized as comprising a Vstator and a rotor each provided Vwith appropriate :windingsfSS and 56 3 respectively, shaft 5 constituting the rotor shaft so that a rotation of the control bow varies the angular position of the rotor windings relative to the stator windings.

The controlled unit of the system is shown as a gun 14, the platform of which supports a rotary shaft 12 on which is fixed a gear 11. This gear meshes with a gear secured to the rotor shaft 9 of a synchronizing device or selsyn unit 8 similar to the synchronizing device 6 and having stator windings 57 and rotor windings 58. As will be evident, the transmission means between shaft 9 and the gun platform are illustrated in a diagrammatic manner only.

The rotor windings 56 of device 6 are connected to an A.C. source 7 and the stator windings 55 and 57 of the two devices are interconnected. However, it would also be possible to feed the A.C. potential to the rotor winding 58 of device 8. As will be apparent, the character of the output signals of the devices is determined by the relative position of the rotors of the devices, or in other words by the relative position of control unit 1 and controlled unit 14. It will further be apparent that the two devices function in the nature of an A.C. selsyn system and any conventional system of this type can be employed.

Shaft 12 is rotated by means of a rotary drive unit 13. The design of this drive unit does not constitute part of the present invention. It suffices to say that it is reversible and adjustable as to speed. The drive unit is symbolized by a block.

The rotor windings 58 of device 8are connected to the input side of A.C. amplifying means 15 of conventional design the output side of which is connected to conventional phase detecting means 16 which are also connected to the A.C. source 7 so that the same A.C. potential is fed to the detecting means as is fed to the rotor windings of device 6. The phase detecting means are followed by D.C. amplifying means 17, filter network means 18 and an output stage 19 which may include an electronic valve coupling of conventional design. All the aforementioned means are connected in a cascade circuit. The output stage 19 is connected with a control device 21 shown as a differential relay. This relay comprises two coils and 23 of which coil 20 is connected in a circuit between one terminal of output stage 19 and ground and coil 23 is connected between the other terminal of output stage 19 and ground. The differential relay further comprises a movable core bar 25 supporting an armature 26 the position of which relative to coils 20 and 23 is controlled by the flow of current through these coils as will be more fully explained hereinafter. The differential relay serves to control the operation of drive unit 13. The operative coupling between the relay and the drive unit is diagrammatically shown as an arm 27 pivoted on one end to bar 25 extending from armature 26 and at the other end to a shaft 28 which should be visualized as controlling the drive unit as to direction and speed in response to a displacement or armature 26 relative to the relay coils. A pointer 29 movable together with shaft 28 and coacting with a scale 30 serves to indicate the speed and rotational direction of the drive unit.

The entire system, as hereinbefore described, is or may be conventional so that it is believed that a detailed description of the drive unit is not essential for the understanding of the invention.

As previously explained, the principal novel feature of the invention resides in the lter network means 18. These means are shown on Figs. 1 and 2 as a cross-filter network, the series arms of which include resistance means 31 and 32 connected in parallel withycapacitance means 34 and 33 respectively. The shunt arm of the network includes resistance means 39 and each of the cross-arms of the network includes resistance means and capacitance means 35, 40, and 37, 38 respectively.

The filter network of Figs. 1 and 2 can be varied in several respects.

Fig. 3 shows a T-network the series arm of which includes resistance means 41 and 42 in series connection and capacitance means 43 connected in parallel across the resistance means. The shunt arm is connected to the junction point between the two resistance means and includes the capacitance means 44 which can also be replaced by resistor means.

The network according to Fig. 4 is a T-network, the series arm of which comprises two resistance means 45 and 46 connected in series and two capacitance means 47 and' 48 connected in parallel across the two resistance means. One shunt arm of the network is connected to the junction point between the two resistance means and includes resistance means 49 and a second shunt arm is connected to the junction point between the two capacitance means and includes resistance means S0.

The T-network of Fig. 5 is a reversal of the network of Fig. 3. Accordingly, the series arm of the network comprises capacitance means 51 and 52 in series connection and resistance means 53 connected in parallel across the capacitance means. The shunt arm of the network is connected to the junction point between the two capacitance means and includes resistance means 54.

The respective components of the lter networks according to Figs. l to 5 and of simliar networks are so designed that all the networks have equal characteristics. These characteristics may be expressed by the following equation:

' wherein:

the magnitude of the The operation of the follow-up system, as hereinbefore described, is as follows:

As previously stated, the envelope or character of the output signal of the rotor of the device 8 is a function of the relative position of the rotors of the two devices or, in other words, a function of the deviation of the position of the controlled unit from the position of the control unit. The system is so adjusted, as is well known for the purpose, that the output signal of the rotor of device 8 has a predetermined value when the position of the controlled unit corresponds to the position of the .control unit. Generally, the system is set for a zero signal when the positions of the two units are synchronized.

The phase detector 16 to which is fed the same A. C. potentia as to the rotor of device 6 generates a positive D. C. signal when the output signal from the rotor of device 8 is in phase with the signal from the A. C. source 7, and a negative D. C. signal is generated by the detector when the signal from the rotor of device 8 is in opposite phase. The D. C. signals are then fed to the D. C. amplifying means 17, the iilter network 18 and the out- `put stage 19. Coils 20 and 23 of diierential relay 21 are so connected to the D. C. amplifier 17 that the D. C. currents flowing throughv the coils are equal when the positions of the controlled unit andthe control unit are equalized, that is, when the gun is in the position demanded by the sight.

Let it now be assumed that detector 16 generates positive direct current. Then, the flow of current through coil is increased and the ow of current through coil 23 is decreased. As a result, armature 26 is attracted by coil 20 thereby actuating drive unit 13 to yoperate in a direction in which the gun is moved toward a position in which the output signalY of the rotor of device 8 becomes zero. The speed with which the drive unit operates and hence the gun is moved depends upon the strength of the output signal from the rotor of device 8. The stronger this signal is the more the amature 26 will be attracted thereby setting the drive unit for a higher speed.

When the current from the detector 16 is negative, armature 26 is attracted by coil 423 andthe gun is moved in the opposite direction again with a speed dependent upon the strength of the signal.

Filter network 18 effects a phase shift of the signals fed to the amplifier 15 `so that the aforementioned desirable phase angle of -l80 occurs at -a high frequency while limiting the amplification power of the network to a moderate Ivalue as the frequencyiucreases. The phase shift is positive and occurs within a narrow frequency range. In this connection it should be mentioned that the term low frequencies Vas herein referred to refers to frequencies within a range of 0-2 cycles/sec, and the term high frequencies ,refers to frequencies within a range of 2*-50 cycles/sec.

Filter network means, as herein described, have the advantage that the amplification produced by the amplifiers in the transmission chain 15 to 19 can be substantially increased beyond the values hitherto permissible. As previously explained, this is highly desirable for rapid movement of the gun or other controlled unit into the position demanded by the control unit. Filter networks according to the invention afford also the .advantage that capacitors and resistors only are used. Components of this type have linear changes and can be inexpensively and accurately manufactured.

While the invention has been described in detail with respect to certain now preferred examples and embodiments of the invention it will be understood by those skilled in the art after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended, therefore, to cover all such changes and modifications in the appended claims.

What is claimed as new and desired to be secured by Letters Patent is:

We claim:

1. A follow-up system for rapidly positioning a controlled unit by a control unit situated at a remote point, the said system comprising electric signal means including selsyn devices, an A. C. source, A. C. amplifying means and phase detecting means operatively connected with the `control unit and the controlled unit and arranged to generate a demodulated A. C. error signal of acharacter variable corresponding to the position of the control unit and the controlled unit relative one to the other, the said signals including low and high frequencies and having a varying phase angle, D. C. amplifying means connected in circuit with said error signal means for feeding the said signal to the input side of the D. C. amplifying means, reversible drive means operatively connected with the controlled unit for moving the latter and included in a control circuit with the D. C. amplifying means for directional control of the drive means by the output signal of the'said amplifying means, and ler network means included in the circuit connections between the D. C. amplifying means and the drive means, the said filter network means effecting a larger positive phase lead of the signal within the frequency range in which the system is subject to self-oscillation whereby the amplitude curve as a function of the frequency is limited to a small increase at frequencies within the said range and at higher frequencies.

2. A follow-up system'fer rapidly positioning g controlled unit by a control unit situated at a remote point, the said system comprising electric signal means including selsyn devices, an A. C. source, A. C, amplifying means and phase detecting means operatively `connected with the control unit and the controlled unit and arranged to generate a demodulated A. C. error signal of a character variable corresponding to the posiijionof the control unit and the cont-rolled unit relative one to the other, the said signals including lowV and high `frequencies and having a varying phase angle, D. C, amplifying means connected in circuit with said signal means for feeding the said signal to the input side vof the D. C. amplifying means, reversible drive means operatively connected with the controlled unit for moving Vthe latter and included in a control circuit with the D. C. amplifying means for directional control of the drive means by the output signal of the said amplifying means, and filter network means included in the circuit connection between the D. C. amplifying mea-ns and the drive means, the components of theV said filter network means being arranged so as to shift signal of high frequency to -a phase angle of -l80 while limiting the increase of the amplitude curve as Va function of the Vfrequency to a value below `the `value at which the system is subject to self-oscillations.

3. A follow-up system as defined 4in claim 1, wherein the components `of the said lfilter network means are selected and adjusted relative one to another so as to satisfy the equation:

wherein V1=input voltage of the network Va=output voltage of the network T1=a constant dependent upon the magnitude of the components of the network T 2=a constant dependent upon the magnitude of the components of the network T 3=a constant dependent upon the magnitude of the components of the network k=a constant dependent upon the magnitude of the components of the networks, the said component being generally less than 1.

w=the angular frequency 4. A follow-up system as defined in claim 3, wherein the said filter network means are in form of a crossfilter network.

5. A follow-up system as defined in claim 4, wherein each series arm of the said cross-lter network includes resistance means and capacitance means in parallel connection.

6. A follow-up system as defined in claim 5, wherein the shunt arm of the said cross-filter network includes resistance means.

7. A follow-up system as defined in claim 6, wherein each of the cross-arms of the said cross filter network includes resistance means and capacitance means in series connection.

8. A follow-up system as defined in claim 3, wherein the said filter network means are in form of a T-network comprising a series arm including two resistance means in series connection and capacitance means connected in parallel across the resistance means, and a shunt arm connected to the junction point between the said two resistance means in the series arm and including capacitance means.

9. A follow-up system as defined in claim 3, wherein the said filter network means are in form of a T-network comprising a series arm including two resistance means in series connection and two capacitance means in series connection and connected in parallel with the resistance means, a first shunt arm connected to the junction point between the said resistance means of the series arm and including resistance means, and a second shunt arm connected to the junction point between the two capacitance means of the series arm and including resistance means.

10. A follow-up system as defined in claim 3, wherein the said filter network means are in form of a T-lter network comprising a series arm including two capacitance means connected in series one with the other and in parallel with resistance means, and a shunt arm connected to the junction point of the said capacitance means and including resistance means.

11. A follow-up system for rapidly positioning a controlled unit by a control unit situated at a remote point, the said system comprising electric signal means operatively connected with the control unit and the controlled unit and arranged to generate a demodulated error signal of a character Variable corresponding to the position of the control unit and the controlled unit relative one to the other, the said signal including low and high frequencies and having a Varying phase angle, drive rneans operatively connected with the controlled unit for moving the latter, electronic chain transmission means connecting the signal means in a control circuit with the drive means, the said transmission means including A. C. amplifying means connected to the signal means, phase detecting means connected to the said amplifying means, D. C. amplifying means connected to the detecting means, and electric control means controlled by the sig- 8 nal output of the D. C. amplifying means and controlling the operation of the drive means in accordance with the character of the said signal, the said D. C. amplifying means including lter network means effecting a large positive phase lead of the signal within the frequency range in which the system is subject to self-oscillation whereby the amplitude curve as a function of the frequency is limited to a small increase at frequencies within said range and at higher frequencies.

Theory of Servo Mechanism, lames, Nichols and Phillips, McGraw-Hill Co., 1947, pp. 114-124.

Servo Mechanism Fundamentals, Lauer, Lesnick Matson, McGraw-Hill, 1947, pp. 158-171.

Electronic Instruments, Greenwood, Holdam, Mac rae, McGraw-Hill, 1948, pp. 329, 340, 341.

Publication of Abstract, Lesnick, 635 O. G. 315, June 6, 1950. 

